I have the following servlet:
public class MyServlet extends HttpServlet {
private static final long serialVersionUID = 16252534;
private static int ping = 3000;
private Thread t;
private static boolean shouldStop = false;
@Override
public void init() throws ServletException {
super.init();
t = new Thread(new Runnable() {
@Override
public void run() {
while(!shouldStop) {
System.out.println("Now:" + System.currentTimeMillis());
try {
Thread.sleep(ping);
} catch (InterruptedException e) {
e.printStackTrace();
}
}
}
});
t.start();
}
@Override
protected void doGet(HttpServletRequest req, HttpServletResponse resp)
throws ServletException, IOException {
super.doGet(req, resp);
System.out.println("doGet");
PrintWriter out = resp.getWriter();
out.println("<html><h1>It works!!</h1></html>");
}
@Override
public void service(ServletRequest req, ServletResponse resp) throws ServletException, IOException {
super.service(req, resp);
System.out.println("service");
}
@Override
protected void doPost(HttpServletRequest req, HttpServletResponse resp) throws ServletException, IOException {
super.doPost(req, resp);
System.out.println("doPost");
}
@Override
public void destroy() {
super.destroy();
System.out.println("Destroy servlet");
shouldStop = true;
}
}
Which is mapped as follows in my web.xml:
<display-name>MyServer</display-name>
<welcome-file-list>
<welcome-file>index.jsp</welcome-file>
</welcome-file-list>
<servlet>
<servlet-name>MyServlet</servlet-name>
<servlet-class>com.myserver.MyServlet</servlet-class>
<load-on-startup>1</load-on-startup>
</servlet>
<servlet-mapping>
<servlet-name>MyServlet</servlet-name>
<url-pattern>/MyServlet</url-pattern>
</servlet-mapping>
When I open my browser (Chrome) on http://localhost:8080/MyServer/MyServlet, then I see “service” from doService() being logged on console and my thread works correctly, however I don’t see “It Works” from doGet() being logged and I get the following error in the browser:
HTTP method GET is not supported by this URL
How is this caused and how can I solve it?
This is the default response of the default implementation of
HttpServlet#doXxx()method (doGet(),doPost(),doHead(),doPut(), etc). This means that when thedoXxx()method is not properly being@Overriden in your servlet class, or when it is explicitly being called viasuper, then you will face a HTTP 405 “Method not allowed” error.So, you need to make sure that you have the
doXxx()method properly declared conform the API, including the@Overrideannotation just to ensure that you didn’t make any typos. E.g.And you also need to make sure that you don’t ever call
super.doXxx()in your servlet method:Your servlet has this. Just get rid of this line and your problem shall disappear.
The
HttpServletbasically follows the template method pattern where all non-overridden HTTP methods returns this HTTP 405 error “Method not supported”. When you override such a method, you should not callsupermethod, because you would otherwise still get the HTTP 405 error. The same story goes on for yourdoPost()method.This also applies on
service()by the way, but that does technically not harm in this construct since you need it to let the default implementation execute the proper methods. Actually, the wholeservice()method is unnecessary for you, you can just remove the entire method from your servlet.The
super.init();is also unnecessary. It’s is only necessary when you override theinit(ServletConfig), because otherwise theServletConfigwouldn’t be set. This is also explicitly mentioned in the javadoc. It’s the only method which requires asupercall.Unrelated to the concrete problem, spawning a thread in a servlet like that is a bad idea. For the correct approach, head to How to run a background task in a servlet based web application?